1. Field of the Invention
The present invention relates to methods and apparatus for measuring and testing the physical properties of materials and more particularly for measuring the elongational viscosity and dynamic surface tension of liquid solutions.
2. Brief Description of the Prior Art
Although various methods exist to characterize the elongational viscosity and to measure the dynamic surface tension of a liquid, none of these methods are conducted within the time scale associated with liquid atomization. This disclosure describes a novel technique from which one can characterize the elongational behavior of a Newtonian fluid or dilute polymer solution, and also measure the dynamic surface tension of a fluid, both within the time scale associated with fluid atomization.
Although other methods of characterizing the extensional flow behavior of a solution exist, e.g. tubeless syphon, impinging jets, falling cylinder, and spin rheometer, only the impinging jet method is suitable for dilute solutions. This method, however, is often unsuitable for low viscosity liquids and polymer solutions due to inertials effects and flow instabilities that occur at higher rates of deformation. Dynamic surface tension measurements are possible using a bubble growth technique, but is also limited to a time scale much larger than that associated with liquid atomization. Thus, in order to investigate the elongational viscosity and dynamic surface tension at high rates of deformation, a novel spray/particle sizing method was developed.
Previous studies of liquid jet breakup in air have established relationships for the resultant particle size, usually, in terms of the Mass Median Diameter (MMD) and as a function of the physical properties of the liquid and air over a range of liquid and air flow rates. In most cases only neat, i.e. fluids without polymer or surfactant additives liquids, have been investigated. When, however, liquid/surfactant blends and dilute polymer solutions are used in jet breakup studies the dynamic surface tension and the elongational viscosity of the polymer solution would affect the resultant MMD.